FI68934B - FELSSTROEMSSKYDDSKOPPLARE SOM REAGERAR AEVEN FOER LIKSTROEMSFELSTROEMMAR - Google Patents

Abstract

1. Fault current safety switch for disconnecting users even in the case of direct current fault currents, which operates with a tripping device, a switch lock and a summation current transformer (1) which comprises a first secondary winding (3) connected to an oscillator (9) and comprises a second secondary winding (4) connected to an excitation winding of a magnetic tripping device, characterised in - that the magnetic tripping device (10) has two excitation windings (16, 17), a first (16) and a second (17), on arms of its yoke (12), - that the first excitation winding (16) is connected to the oscillator (9), the second excitation winding (17) being connected to the second secondary winding (4), and - that the two excitation windings (16, 17) are tuned to one another in such manner that on operation of the oscillator (9), the magnetic fluxes produced by said excitation windings in the magnetic circuit of the magnetic tripping device (10) in the fault current free state, are unidirectional and opposite in relation to one another.

Description

* j £ * r * \ ANNOUNCEMENT. Q

B 11 UTLÄGGNINGSSKRIFT 68 9 34 C (45): '· - * J j (51) Kv.lk.4 / lnt.CI, 4 H 02 H 3/33 (21) Patent application - Patentansoknlng 800939 (22) Application date - Ansökningsdag 26.03 · 80 (EN) (23) Start date - Glltighetsdag 26.03.80 (41) Has become public - Blivlt offentllg 27.09.80

National Board of Patents and Registration of Finland Date of publication | 31 .07.85

Patent and ocean registration '' Ansökan utlagd och utl.skriften publlcerad (32) (33) (31) Privilege requested - Begird priority 26.03.79 Japan-Japan (JP) 54-35270 (71) Fuj i Electric Co., Ltd. , 1-1 Tanabeshinden, Kawasaki-ku, Kawasaki 210,

Japan i-Japan (JP) (72) Shouichi Yamakl, Tochigi, Japan-Japan (JP) (7M Oy Kolster Ab (5 * 0 Fault current protection switch that also reacts to direct current faults - Felsströms-skyddskopplare, som reagerar även för 1ikströmsfelströmmar

The invention also relates to a residual current device for disconnecting users in the event of direct current faults, which switch operates by means of a trigger, a catch and a sum current transformer having a first secondary winding connected to the oscillator and a second secondary winding connected to the magnetic trigger excitation windings.

Recent advances in electrical engineering, with an increasing number of instruments having DC components and a trend towards higher voltages, have created a growing need for suitable RCDs that can respond to DC fault currents.

The majority of RCDs on the market operate on the principle that the RCD causes a residual non-zero in the sum transformer so that a voltage is induced in the secondary winding, which triggers the shutter and switches off the current. Because DC components cannot induce voltage in the secondary windings, such RCDs do not respond to DC RCDs.

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RCDs previously described in the literature, which also respond to DC RCDs, are usually complex and require extensive electronics.

The object of the invention is to develop a residual current device which, in principle, operates by means of a reliable magnetic trigger and can react to a direct current fault current essentially with an oscillator which is commercially available.

The described function can be solved by a residual current device, which is characterized by - that the magnetic trigger yoke branches have two excitation coils, first and second, so that when the oscillator operates, the magnetic fluxes generated by them in the magnetic circuit of the magnetic trigger in the fault-free state are unidirectional and opposite to each other.

When no fault current occurs, the oscillator first acts on the first excitation coil of the magnetic trigger directly and secondly on the second excitation coil through both secondary windings located in the core of the solar current transformer, which act as the primary and secondary windings of the transformer. The magnetic fluxes induced in the magnetizing circuit of the magnetic trigger are then equalized in amount and direction so that in a conventional holding magnet, the magnetic flux passing through the yoke and the anchor can hold the anchor against the force of the trigger spring.

The direct current fault current induces a magnetic flux in the core of the total current transformer, which moves the operating point, so that the signal is transmitted attenuated through both secondary windings. In this case, the magnetic balance of the magnetic trigger is disturbed and the second excitation coil can conduct a current through the magnetic circuit, which smooths out the effect of the permanent magnetic circuit, so that the anchor can fall off the yoke. The falling anchor can open the latch in a conventional manner, thereby severing contact with the monitored lines passing through the sum current transformer.

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It is advantageous if the total current transformer is saturated with the expected DC fault current. In this way, in the case of a fault current comprising direct current, the transmission of the oscillator signal via both secondary windings to the sum current transformer is particularly strongly reduced.

It is preferable to connect the first secondary winding and the first excitation winding of the oscillator in series.

The invention is explained in more detail by means of a schematically illustrated embodiment.

Figure 1 shows a circuit diagram of a residual current device.

Figure 2 is a diagram illustrating the transition from the first secondary winding to the second when no fault current is present. The ordinate describes the magnetic flux and the abscissa describes the magnetic field strength.

Fig. 3 shows, by means of Fig. 2, a residual current circuit breaker for a residual current having a direct current component.

The RCD according to Fig. 1 has a sum current transformer and 1 with an annular core 2. A first secondary winding 3 and a second secondary winding 4 are placed on the annular core. The monitored conductors 5 have switches 8. An oscillator 9 is connected to the monitored supply lines 5 on the load side after the switches 8. This conventional oscillator produces an AC voltage with a frequency higher than the mains frequency. The switches 8 are acted upon in a known manner by a magnetic trigger 10. When the anchor 14 opens, a latch can open in a normal manner, which opens the switches 8. The magnetic trigger 10 can be a polarized relay or a holding magnet. Typically, it has a permanent magnet 11 and a magnetic parallel connection 13. However, it is essential that two excitation coils 16 and 17 are placed on the magnetic trigger yoke 12, which are connected in a special manner to the two second coils 3 and 4 of the sum current transformer and the oscillator 9. the first secondary winding 3 is connected in series with the output of the oscillator 9 and the first excitation winding 16. The second secondary winding 4 is connected to the second excitation winding 17.

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By means of the magnetic parallel connection 13, the magnetic flux of the anchor 14 can be adjusted so that the anchor remains securely in place against the spring force of the trigger spring 15 in the absence of a fault current.

The excitation coils 16 and 17 are arranged so that, when the oscillator 9 is operating, the magnetic fluxes produced by them in the magnetic circuit of the magnetic trigger 10 in the fault-free state are unidirectional and opposite to each other. In this case, the magnetic state provided by the permanent magnet 11 in the yoke 12 and the anchor 14 remains unchanged. In the error-free state, the output voltage of the oscillator 9 passes once through the secondary winding 3 and 4 of the sum current transformer 1 as a voltage V2 to the second excitation coil 17 and second directly to the first excitation coil 16. The current IH induces the voltage V2 to the first secondary winding.

The diagram of Figure 2 shows how the secondary windings 3 and 4 on the core 2 of the sum current transformer 1 function as the primary and secondary windings of a conventional transformer. The ordinate describes the magnetic induction and the abscissa describes the magnetic field strength. The magnetic characteristic curve is affected by the alternating current IH flowing from the oscillator 9 to the first secondary winding 3. In this case, a magnetic induction B and on the secondary side, i.e. a corresponding voltage V2 at the output of the second secondary winding 4, are generated. In Figure 2, the magnetic characteristic in the operating range is simplified to a straight line. The magnetic flux B generated by the alternating current IH induces the voltage V2 on the secondary side.

When the summing current 1 is magnetized due to the fault current of the magnetic core 2, the operating point shifts with respect to both secondary windings 3 and 4, because the rest of the magnetic characteristic curve is not straight. Preferably, however, magnetic saturation can also be used.

In the core 2 of the sum current transformer, which is saturated by the fault current, the situation according to Fig. 3 prevails. The fault current, in your execution example, the fault direct current 1G, affects the shown transition of the operating point to the saturation part of the magnetic characteristic. In the second secondary winding 4, which is in the position of the embodiment according to Fig. 1, only a lower voltage V2 'then passes from the alternating current IH through the first secondary winding 3 to the second secondary winding 4. It will be appreciated that this voltage drop will also occur with respect to the operating state of Figure 2 if, for example, there is a DC fault current greater than that shown in Figure 3, i.e. greater than the saturation fault current.

If the RCDs 8 are closed in the RCD according to Fig. 1, the oscillator 9 starts to operate. It excites with the alternating current IH the first secondary winding 3 of the sum current transformer 1 and the first excitation winding 16 of the magnetic trigger 10. In this case, a voltage V2 also develops in the second secondary winding 4, which in this case is the actual secondary winding and adjacent to the second excitation winding 17 of the magnetic trigger.

In the fault-free state, the magnetic flux generated by the second excitation coil 17 cancels out the magnetic flux of the excitation coil 16. In this case, the magnetic flux generated by the permanent magnets 11 in the yoke 12 and the anchor 14 remains unchanged.

When a leakage current occurs in the monitored line, the sum of the voltage V2 induced in the second secondary winding 4 of the current transformer 1 decreases to a lower value V2 ', so that the magnetic flux generated by the second excitation coil 17 decreases accordingly. However, the magnetic flux generated by the exciter coil 16 remains unchanged, so that the magnetic balance now ceases. In the magnetic trigger 10 formed by the polarized relay, the present magnetic exchange current during the new half-wave is known to attenuate or suppress the permanent magnetic flux. In this case, the anchor 13 falls in this half-wave, whereby the switches 8 open.

In the RCD according to the invention, the core of the sum current transformer of the RCD is preferably saturated with the RCD, which should be triggered.

Claims (3)

6 68934 A residual current device for disconnecting users also in the event of direct current faults, which switch is actuated by a trigger, a catch and a sum current transformer (1) having a first secondary winding (3) connected to the oscillator (9) and a second secondary winding (4) connected to the excitation coils of the magnetic trigger, characterized in that - the branches of the yoke (12) of the magnetic trigger (10) have two excitation coils (16, 17), a first (16) and a second (17), - the first excitation coil (16) is connected to an oscillator ( 9), wherein the second excitation coil (17) is connected to the second secondary winding (4), and - that both excitation coils (16, 17) are tuned relative to each other so that the oscillations generated by the oscillator (9) in the magnetic circuit of the magnetic trigger (10) the magnetic fluxes are unidirectional and opposite to each other. Residual current circuit breaker according to Claim 1, characterized in that the core (2) of the sum current transformer (1) is saturated by the DC fault currents to be examined. RCD according to Claim 1, characterized in that the first secondary winding (3), the oscillator (9) and the first excitation winding (16) are connected in series.